A capacitively phase-coupled low noise, low power 0.8-to-28.2GHz quadrature ring VCO in 40nm CMOS

This paper presents a novel tunable wide-operating range capacitively phase-coupled low noise, low power ring-based voltage controlled oscillator (VCO) for use in multi-GHz phase-locked loops (PLLs). The basic building blocks of the ring oscillator (RO) design are discussed along with a technique to expand the VCO to a variety of phases and frequencies without the use of physical inductors. Improved performance with minimal phase noise are achieved in this ring VCO design through distributed passive-element injection locking (IL) of the staged phases via a network of symmetrically placed metal interconnect capacitors. Using this method, a 0.8-to-28.2 GHz quadrature ring VCO was designed, fabricated, and physically tested with a PLL in an all-digital 40nm TSMC CMOS process. Most notably the proposed quadrature VCO occupies an area of 0.0024mm², consumes a power of 0.88mW at a 1.0V supply voltage, and possesses a phase noise of -124.5dBc/Hz at the 10MHz offset for a carrier frequency of 28.0GHz.